As a gas guy, some of these responses are hilarious and I'll have to use some of them in the future.

Kind of surprised anyone would install black iron outside, we use galvy. Use a metal paint scraper on the pipe and coat it with any outdoor paint, preferably something designed to be applied to rust. I can't remember the stuff we use but it has a red stop sign and the word rust on it. Yellow is a good color for gas.

It really should have been galvy or wrapped with 10mil, however iron pipe is pretty durable and unlikely to rust through in your lifetime.

Hmm, down here when we come across galvanized we eliminate it due to flaking of impurities inside the piping. Not as bad as copper, but it's a code nono.